I think she didn't smile much early on because she was getting a bit turned on by the modeling, at least that was the impression I got.
Maybe. I tend to think it was mostly just nerves. She was so adorable and bubbly in that intro video for her site, but it took her a while before that personality would shine through in the videos. Now Sofia on the other hand, was a natural exhibitionist. From the beginning you could tell she loved to tease, was great at is, and was having the time of her life making these videos. Her "String Thing" video is legendary, and she got even hotter when for a while she would talk a little bit in her videos. One of my favorite moments is in the one where she's posing in that tiny denim outfit next to the lake, she says, "There's currently boaters watching me," and gives a cheeky smile. And at the end of her Christmas video:
"Merry Christmas, *blows kiss*, from your naughty little girl herself."
Man, she was something else.